JPH07106538A - Manufacture of solid-state image sensing device - Google Patents

Abstract

PURPOSE:To provide a manufacturing method capable of manufacturing solid- state image sensing devices having microlenses and cover glasses or prisms for a short time easily. CONSTITUTION:After the formation of photodiodes 2 on a semiconductor substrate 1, a thin film 3 is formed on the whole surface out of transparent material. Following this, a silicon oxide film is formed and then ions are implanted into the silicon oxide film from the surface by ion implantation. After a resist film is applied to the surface, openings are formed in the photodiode parts. Next recessions are formed in the silicon oxide film by wet etching, and the resist film is removed. Following this, anisotropic etching is performed from the surface on condition that the etching rate of the silicon oxide film becomes equal to that of the thin film 3, and transfer recessions 8a are formed in the thin film 3. Following this, a cover glass or prism 9 is glued on to the thin film 3 using an adhesive 10 of a high refractive index.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid-state image pickup device, and more particularly to a method for manufacturing a solid-state image pickup device having a microlens and a cover glass or a prism for improving sensitivity.

[0002]

2. Description of the Related Art Generally, CCD and CMD (Charge Modul)
In the solid-state imaging device using a photoelectric conversion device, etc., since the semiconductor main surface is provided with the photoelectric conversion unit and the signal readout unit, the area actually contributing to photoelectric conversion is limited to about 20 to 50%. . As a means for solving this drawback, a method of providing a microlens for condensing each pixel for condensing incident light on a photoelectric conversion part is disclosed in JP-B-60-5975.
It is proposed in Japanese Patent Publication No. 2 and the like.

FIG. 7 is a sectional view showing the structure of a pixel portion of the solid-state image pickup device with the microlens described in the above publication. In FIG. 7, 11 is a silicon substrate, 12 is a channel stop, 13 is a diffusion layer, and 14 is a diffusion layer. Is a photodiode, 15 is an insulating film,
Reference numeral 16 is a polysilicon gate, and 17 is a microlens converging body made of an organic material such as photoresist. With this structure, incident light in the range D is photodiode 14
It is designed to be illuminated.

[0004]

By the way, depending on the application of the solid-state imaging device, as shown in FIG. 8, a cover glass 19 and a cover glass adhesive layer 18 are provided on the solid-state imaging device with the microlens shown in FIG. It may be required to be formed. Furthermore, in the case of clear mold mounting, the clear mold material is formed in contact with the microlens. With such a structure, the refractive index of a microlens made of a normal organic material is about
On the other hand, the refractive index of the cover glass adhesive layer or the clear mold material is close to that of the microlens material, so that the microlens effect is significantly reduced.

In order to improve this point, JP-A-58-22
Japanese Patent Laid-Open No. 0106 discloses a structure of a microlens suitable for mounting a clear mold or the like. FIG. 9 shows an embodiment disclosed in the publication, in which 21 is a semiconductor substrate, 22 is a photodiode formed in the semiconductor substrate 21, 23 is an oxide film, and 24 is a glass having a concave shape, resin, or the like. Thin film, which is filled with the concave portion of the thin film 24, has a translucent thin film
It is a material having a refractive index higher than 24. With the configuration shown in FIG. 9, the incident light 26 is effectively focused on the photodiode 22 by the microlens effect of the filling material 25 and the thin film 24. However, in this publication, the thin film 24 is made of a resin, while the filling material 25 in the recess of the thin film 24 is only a translucent material, and no specific material is disclosed.

Further, Japanese Laid-Open Patent Publication No. 62-23161 discloses a method of manufacturing a microlens suitable for clear mold mounting, similar to that shown in FIG. 9, and its construction will be described with reference to FIG. explain. In FIG. 10, 31 is a photodiode portion formed in silicon, 32 is a thin film having a concave shape made of a silicon oxide film, and 33 is a lens made of silicon nitride. The method for forming the lens 33 made of silicon nitride involves first depositing thick silicon nitride by a CVD method or the like and then flattening the surface by an etch back method, which is a complicated process step. It had drawbacks.

The present invention has been made in order to solve the above-mentioned problems in the conventional solid-state image pickup device having a microlens. Even when a cover glass or a prism is provided, the lens effect does not disappear. It is an object of the present invention to provide a method for manufacturing a solid-state image pickup device that can easily form a microlens and can be downsized.

[0008]

In order to solve the above problems, the present invention provides a plurality of photoelectric conversion elements arranged in a matrix on the surface region of a semiconductor substrate, and each of the photoelectric conversion elements on the semiconductor substrate. In a method for manufacturing a solid-state imaging device, each of which includes a microlens that converges incident light in a portion corresponding to a photoelectric conversion element, a low-refractive-index transparent substrate having a concave portion corresponding to each photoelectric conversion element on the semiconductor substrate A film is formed, and a cover glass or a prism is adhered onto the transparent film with a transparent adhesive having a higher refractive index than the transparent film.

After forming the low refractive index transparent film having the concave portion in this way, the cover glass or the prism is adhered by the transparent adhesive having the high refractive index, whereby the high refractive index adhesive is transparent. The microlenses are easily and quickly formed with the adhesion of the cover glass or the prism.

[0010]

EXAMPLE An example of a method of manufacturing a solid-state image pickup device according to the present invention will be described below with reference to the manufacturing process diagrams shown in FIGS. First, as shown in FIG. 1, a transparent material for forming a large number of PN junction photodiodes 2 forming pixels arranged in a matrix on a semiconductor substrate 1 and forming a concave structure therein on the surface of the semiconductor substrate. A thin film 3 made of is provided. In the present embodiment, the transparent material forming the thin film 3 has a low refractive index such as a trade name "CYTOP" made of a fluorine resin (the refractive index value of CYTOP is about 1.35). Things are used.

A method for forming a recess in the thin film 3 is described in the above-mentioned JP-A-58-220106 or JP-A-62-23161.
Although various methods are conceivable in addition to the method disclosed in the publication, in this embodiment, the recess forming method using the ion implantation method and the wet etching method is used, which will be described next. First, as shown in FIG. 2, after forming the thin film 3, the silicon oxide film 4 is formed on the thin film 3 in a low temperature state that does not damage the thin film 3. As a method of forming this silicon oxide film 4, ECRCVD (Electron C
ycrotron Resonance Chemical Vapor Deposition) method or S.I. O. A G (Spin On Glass) method or the like can be used.

After the silicon oxide film 4 is formed, ions 5 are implanted from the surface by the ion implantation method. By this ion implantation process, the etching rate at the time of wet etching of the silicon oxide film 4 increases toward the surface. Next, as shown in FIG. 3, a resist film 6 is applied to the surface of the wafer by a photolithography method, and a portion corresponding to the center of the photodiode 2 is formed by the next exposure / development process.
The opening 7 having a desired size is formed. Then H
A recess 8 is formed in the silicon oxide film 4 as shown in FIG. 4 by an F-based wet etching method. As described above, the silicon oxide film 4 has a property that the etching rate becomes larger as it gets closer to the surface by the ion implantation process, so that the curved concave portion 8 having an aspect ratio of 1/2 or less can be formed. Therefore, when the optimum recess shape is set by optical design, conditions such as acceleration energy and dose amount of the ion implantation method may be set so that the optimum recess shape can be formed by the wet etching method. .

Next, after the silicon oxide film 4 having the cross-sectional shape shown in FIG. 4 is obtained, the resist film 6 is removed, and then the etching conditions are set so that the etching rates of the silicon oxide film 4 and the thin film 3 become equal. , From the surface. I. E (Reac
When anisotropic etching is performed by the tive ion etching method (etch back step), as shown in FIG. 5, the surface shape of the silicon oxide film 4 in which the recess 8 is formed is transferred to the thin film 3 and the thin film 3 is formed. The transfer recess 8a is formed. After completion of this step, an image sensor inspection step is performed, and after the wafer scribing step, non-defective chips are transferred to the assembly step.

Subsequently, as shown in FIG. 6, the lower surface of the cover glass or the prism 9 is adhered onto the thin film 3 with an adhesive 10. A material that is transparent to visible light and has a refractive index higher than that of the thin film 3 is used for the adhesive 10.
It is preferably 1.7 to 1.8 or more. Examples of the adhesive having such a high refractive index include epoxy-based or polyimide-based thermosetting resins.

Then, the adhesive 10 causes the transfer recess 8a of the thin film 3 to be transferred.
By having the structure shown in FIG. 6 filled in
Similar to a solid-state imaging device in which a convex lens is provided on the outermost surface of an ordinary chip and hermetically sealed, the light-collecting effect of the on-chip microlens is obtained, and the sensitivity is improved.

When the solid-state image pickup device thus constructed is used for a single-plate color camera, a color filter group is formed in or under the thin film 3. Further, when used for a three-plate color camera, the transparency of the adhesive is required to transmit light corresponding to each color, but it is not necessary to transmit other light.
In the case of a single-plate color camera, when the adhesive has a light transmission characteristic that changes depending on the wavelength, the color filter group may be designed and formed in consideration of the transmission characteristic of the adhesive.

In the above embodiment, the present invention is applied to the solid-state image pickup device having the PN junction photodiode, but the present invention can also be applied to the solid-state image pickup device having the MOS photodiode. is there.

[0018]

As described above on the basis of the embodiments,
According to the present invention, a solid-state imaging device including a microlens and a cover glass or a prism can be easily manufactured in a short time, and a cover glass or a prism can be formed on a chip without passing air. Therefore, the solid-state imaging device including the mounting package can be downsized without impairing reliability.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process for explaining an embodiment of a method for manufacturing a solid-state imaging device according to the present invention.

FIG. 2 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG.

FIG. 3 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 2;

FIG. 4 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 3;

FIG. 5 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 4;

FIG. 6 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 5;

FIG. 7 is a cross-sectional view showing a configuration example of a conventional solid-state imaging device including a microlens.

FIG. 8 is a cross-sectional view showing a configuration example of a conventional solid-state imaging device including a cover glass.

FIG. 9 is a cross-sectional view showing a configuration example of a conventional solid-state imaging device including a microlens suitable for clear mold mounting.

FIG. 10 is a cross-sectional view showing another configuration example of a conventional solid-state imaging device including a microlens suitable for clear mold mounting.

[Explanation of symbols]

 1 Semiconductor Substrate 2 Photodiode 3 Thin Film 4 Silicon Oxide Film 5 Ion 6 Resist Film 7 Opening 8 Recess 8a Transfer Recess 9 Cover Glass or Prism 10 Adhesive

Claims (1)

[Claims] 1. A plurality of photoelectric conversion elements arranged in a matrix on a surface region of a semiconductor substrate, and a microlens for converging incident light to a portion corresponding to each photoelectric conversion element on the semiconductor substrate, respectively. In the method for manufacturing a solid-state image pickup device, a transparent film having a low refractive index having concave portions corresponding to the photoelectric conversion elements is formed on the semiconductor substrate, and a cover glass or a prism is provided on the transparent film. A method for manufacturing a solid-state imaging device, which comprises bonding with a transparent adhesive having a higher refractive index than that of.